Gas conduction device



y 1, 1934- G. w. GARMAN ,957,205

GAS CONDUCTION DEVICE Fiied March l, 1952 2s: a0 j 1; I4 2: g

55 E? a l 45 N 433 A l 44 V 41W MM In vntor: George W. Gar-m an,

by m

His Attorney.

Patented May 1, 1934 STATES GAS CONDUCTKON DEVKCE George W. Gar-man, Scotia, N. 1 assignor to General Electric Company, a corporation of New York Application March 1, 1932, Serial No. 596,065

4: Claims.

The present invention relates to the control and variation of luminosity of positive column lamps, such, for example, as neon lamps and mercury vapor lamps. It is the object of my invention to provide an apparatus or system whereby such lamps may be economically operated under conditions rendering the variation of luminosity and control of such lamps convenient.

In lighting systems employing positive column lamps (hereafter referred to as discharge lamps) it is sometimes desired to produce striking lighting effects by varying the light emission. For example, when employing sets or combinations of neon lamps and mercury vapor lamps, pleasing lighting effects may be produced by causing the respective lamps to become dim and bright in a cyclic succession of changes. For example, the light from such an output as a whole may be caused to vary from predominant red color (neon) to a white effect (combination) and then to a predominate bluish-green color (mercury vapor). When such glow lamps are operated from a direct current supply circuit in series with resistances, and the desired variations in light output are produced by varying the value of series resistances, the over-all efficiency of such a system will be low.

In accordance with my invention I have provided an alternating current system for operating such lamps, or equivalent devices, which is simple and reliable and of higher efficiency than such a direct current system. This improved system includes a variable impedance in the main alternating current circuit, and provides an auxiliary electrode in the gaseous discharge device whereby by direct current excitation a relatively small exciting current is caused to flow in the gaseous discharge path of the lamp or equivalent device. As will be later more fully explained, by the use of this auxiliary exciting current a lower alternating current voltage, and a smaller impedance may be used in the main circuit in order to effect a desired con trol of light output and hence a higher efliciency of operation results.

The accompanying drawing, Fig. 1, illustrates diagrammatically an embodiment of my invention. Only one lamp circuit is illustrated but my invention may be utilized with a combination of unlike lamps to produce various colored lighting effects as above indicated. Figs. 2 and 3 are graphs illustrating current and voltage relations under different conditions.

Referring to the drawing, the system illustrated includes a lamp comprising an elongated envelope 1 made of glass, fused quartz, or the like, and containing a luminosity-producing medium as for example, neon, argon, helium, mercury vapor, or other gas or vapor, or mixtures of such. The pressure ordinarly will be within the range of about one to ten millimeters of mercury. The lamp contains main anodes 2, 3, which are located in side arm branches of the envelope, and a main cathode 4 which preferably but not necessarily is of the thermionic type. In the case of the lamp shown, the cathode comprises a shell of nickel, iron, or other suitable metal, coated inside, or outside, or on both sides with a thermionically active material such for example as barium oxide. The cathode is provided with a resistance heater 5. which is connected to a heating circuit 6, 7 through the intermediary of the shell 4. The heater 5 is supplied with energy by the secondary winding of a transformer 8. A direct current lamp of this general type is disclosed in Hull Patent 1,790,153 patented January 27, 1931. A novel feature of the lamp shown in the drawing is an aux'liary anode 9 located at the end'of the envelope remote from the cathode. Between the cathode 4 and the auxiliary anode 9 there is connccted a direct current supply circuit 11, 12. The positive conductor 12 contains a resistance 13. The negative conductor 11 is connected to an intermediate point on the main transformer 14 and from thence is connected in series with a switch 15 and a solenoid 16 to the cathode conductor 6. The armature 1'7 of this solenoid 16 is connected mechanically to a mercury switch 18 in a starting circuit to be described later. The anodes 2, 3 of the lamp are connected respectively by the conductors 20, 21 to the secondary of the main transformer 14- (shown as an auto-transformer). Resistances 22, 23 preferably are included in the anode circuits as shown. The cathode is connected by a part of the conductor 11, the mercury switch and the conductors 25, 26 to the anode conductor 20 in series with a resistance 27, and the terminals of a contactor 28. The solenoid for operating this contactor is conected in circuit with the auxiliary anode 9 in the circuit 12. The primary winding of the transformer 14 s supplied with alternating current by the conductors 29, 32. Energy is supplied to the primary winding of the cathode heating transformer 8 through the conductors 30, 31.

In circuit with the alternating current supply conductor 32 is a winding 33 of an iron cored impedance device 34. A second winding 35 namely the saturating winding of this device or saturable core reactor is connected by the conductors 36, 37 in series with a variable resistance 38 to the direct current circuit 11, 12.

In a system such as above described when the switch 15 is closed (both the alternating and direct current circuits being energized) the core 17 of the solenoid 16 is drawn down causing the mercury switch 18 to break its circuit and impressing a high voltage impulse on the electrodes 2. 4, from the portion of the transformer secondary winding between the conductors 11, 20. This high voltage impulse starts the main gaseous ionization discharge in the lamp which then operates between the cathode and the anodes 2, 3 alternately. Direct current supplied by the conductors ll, 12 also begins to flow between the cathode 4 and the auxiliary anode 9. This current energizes the winding of the contactor 28, which operates to open the starting circuit 25, 26.

The light output of the lamp may be varied over a wide range, say from ten amperes down to one-tenth ampere or even less, by varying the ellective value of the impedance device 34. In the example illustrated this is done by varying the resistance 38 one terminal of which is movable. The luminosity-producing auxiliary discharge has too low a luminosity to materially interfere with the dimming of the lamp.

When in systems heretofore employed containing a lamp similar to that shown in Fig. 1 but without an auxiliary anode, the current in the gaseous discharge device has been reduced to a value below a limiting value the discharge becomes extinguished. Above this limiting value, the tube current and hence the light output may be varied. This relation is illustrated by the graph constituting Fig. 2. The current fluctuations are evident from the current curve 41, the base or zero line of current being the line 42. The corresponding voltage between anodes is indicated by the curve 43, on the zero line 44. It will be observed (although this fact has no bearing on the present invention) that between the cyclic reversals the voltage becomes substantially zero for short periods. During these periods current is flowing from both anodes to the cathode. When the operating current and hence the light output heretofore were varied by a series resistance approximatly fifty per cent of the total power input was dissipated unavoidably.

In a system embodying my invention variations of continuously flowing current also can be produced as in the case of a resistance-controlled system with resulting greater economy. It is possible, however, to operate at lower current values at which the current becomes discontinuous as illustrated by the graph forming Fig. 3. It will be seen that the current curve 45 on the base line 46 falls periodically to zero. The voltage curve 47 on a base line 48 is shown above the current curve.

Although, as shown in this figure, the current becomes substantially discontinuous (except for the continuously flowing current to theauxiliary anode 9), the light emission has the appearance of continuity and steadiness to the eye. The level of luminosity hence may be decreased to lower values than in the case illustrated by Fig. 2.

The efilciency of the new system constituting my invention is relatively high. The energy dissipated by the holding are or discharge is very small. The current need be only about 10 milliamperes at 250 volts. It is not necessary that a large impedance shall be used for control purposes.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A lighting device comprising the combination of a gaseous discharge lamp having a positive column discharge path, alternating current means for operating said lamp, means connected to said lamp for varying the luminosity thereof and means for producing an auxiliary discharge substantially throughout said discharge path for maintaining the discharge path conductive dur ing the periods when the value of the alternating current is reduced below the value required to maintain said discharge path conductive.

2. In combination, an electric discharge device which contains a luminosity-producing agent and is provided with main electrodes and also an auxiliary electrode, an alternating current supply circuit connected to said main electrodes, an impedance device in said circuit, means for varying said impedance, and a direct supply current connected to said cathode and said auxiliary electrode.

3. The combination of a discharge lamp containing electrodes including a thermionic cathode, alternating current means for producing a luminosity-producing discharge between said electrodes, means for maintaining continuously therein an auxiliary discharge of such low current value that the luminosity produced thereby is negligible, and means for varying the discharge between said main electrodes'to vary the light output of said lamp.

4. In combination, a positive column lamp which contains a luminosity-producing gas, and

is provided with main electrodes and also an aux- 

